The present invention relates to the field of data communications, and more particularly to the field of data communications using connections over a telephone network.
Due to the growing popularity of the Internet, modems have become standard components in personal computers. Users initiate data connections over the public switched telephone network by dialing up to Internet service providers. The Internet service providers typically have a bank or pool of modems that respond to the connections initiated by users and connect the users to the data networks that make up the Internet. Once connected, the users have access to a wide variety of services that may communicate information using graphics, sound, animation, and other multimedia features.
The accessibility of the Internet contributed to its success. The accessibility of the Internet may be attributed to the reach of the public switched telephone network. The public switched telephone network has evolved and become so extensive that telephone service is considered a basic utility. Because most people have a telephone network connection, most people can connect to the Internet by using a modem. Other ways to communicate with the Internet are available. As discussed below, however, many require additional equipment in the user""s premises and in the telephony infrastructure. Connections through the telephone network require nothing more than a modem.
Modems are communications systems that convert telephony signals to data signals. Modems are systems that have an analog front end that communicates analog signals over the public switched telephone system and a digital back end that communicates data with a data system. The analog front end includes an analog-to-digital converter that converts the analog telephony signals to digital form. The front end sends the digital signals to the back end for processing as data. The back end converts the data to digital signals to send to the front end. The back end may also include high-level functions such as data compression, error detection and correction and other modem functions. The analog-to-digital converter converts the digital signals it receives from the back end to analog signals and sends the signals over the public switched telephone network.
Modems typically operate in environments in which space is a premium, such as in personal computers, or in laptop computers, or in a bank or pool of modems. Modem designers therefore attempt to keep the physical size of modems to a minimum. In addition, the bandwidth requirement for the connection between the front half and the back half of modems is typically high. Due to over-sampling by the analog to digital converter, the connection is designed to carry signals at several times the data rate of the modem. For example, the connection of a 56 k bits/sec modem may carry 3 times the 56 k bits/sec, or 168 k bits/sec. To meet physical space and bandwidth constraints, the front half and back half of modems are built to operate in the same module, which may be the same circuit board, or even the same piece of silicon.
Each data connection is a telephone connection that uses two modems: the user""s modem and the Internet service provider""s modem.
The user""s modem is connected via a subscriber line to a local switch. The switch may connect the call via inter-office trunking, and optionally, via one or more intermediate switches, to another switch local to the Internet service provider. The switch then uses a subscriber line to connect to the service provider equipment, which includes the second modem in the connection. Data connections typically involve subscriber loops between the user and the local switch and between the service provider and the same or another local switch. The bandwidth of the subscriber loop connections is limited to the 64 kbits/sec bandwidth of the telephone lines. The data rate of the modems that connect to the telephone network analog lines is limited to the 64 kbits/sec available on the telephone lines.
It would be desirable to connect to the Internet or other data network at data rates that are faster than the 64 kbits/sec limitation of the telephony infrastructure.
Several systems have been developed to overcome the 64 kbits/sec bandwidth limitation. Digital subscriber lines (DSL) and the Integrated Digital Services Network (ISDN) provide connections with substantially higher data rates than 64 kbits/sec while off-loading data traffic from the telephone network. These solutions, however, require special equipment at the customer""s premises and at the central office in which the switch that services the customer""s service area is located. For example, DSL requires that a pre-switch adjunct be located in close proximity to the local switch to divert data traffic away from the interoffice trunks. The pre-switch adjunct is added in front of the switch (or before the switching functions are used) to connect a subscriber line directly to a data network through a remote access server, or other piece of equipment.
One desirable solution may be to install the second modems of data connections in remote digital terminals, or in other equipment that presently exists in locations that are between the customer and the switch. Remote digital terminals and other intermediate telephony equipment typically has higher data rate (e.g. DS1, DS3, OC1, OC3, OC9, etc.) connections. Because the equipment is closer to the customer than the switch, it may be feasible to connect high-speed data lines from the customer""s modem to the modems in the intermediate telephony equipment. The special data equipment would then connect the data lines to the DS1 or DS3 lines.
One problem with this solution is that the modems in the intermediate equipment to which the high-speed data lines are connected have technical requirements that may not be adequately met by the telephony infrastructure. The digital processing components in the modems require operating conditions that may not exist in the intermediate equipment structures. The heat dissipation, power and space requirements of the modems used for high-speed data access tend to be different from the traditional telephony signals communicated by the telephony equipment. Much of the telephony equipment is installed in environments that may be too harsh for the modems. The present telephone infrastructure makes it difficult to allocate data communications resources where it would provide high-speed data access.
In view of the foregoing, it would be desirable to provide high-speed data access that is not limited to the bandwidth set by the telephone infrastructure.
It would be further desirable to provide high-speed data access without requiring data equipment to operate in the harsh environments that were intended only for telephony equipment.
It would be further desirable to off-load data traffic from the telephone network without requiring the insertion of new equipment at the local digital switch.
In view of the above, the present invention is directed to a communications system for communicating data between a data system and a user connected to a subscriber line. The system includes a first module communicably connected to the subscriber line to receive a first analog signal. The first module also sends a second analog signal back over the subscriber line. The first module includes a first digital connection for sending a first digital signal and for receiving a second digital signal. A signal converter converts the first analog signal to the first digital signal and the second digital signal to the second analog signal.
The system includes a second module, physically separate from the first module and communicably connected to the data system. The second module includes a second digital connection for receiving the first digital signal and for sending the second digital signal. A signal processor processes the first digital signal received from the second digital connection as a first data stream. The second module sends the data stream to the data system and processes a second data stream received from the data system as the second digital signal. The second module sends the second digital signal to the second digital connection. An interconnection path connects the first module to the second module. The interconnection path communicates the first and second digital signals between the first digital signal connection and the second digital connection.
In another aspect of the present invention, a method is provided for communicating data between a user at a subscriber line and a data network. In a first module, an analog signal at the subscriber line is converted to a digital signal. The digital signal is analyzed to determine if it includes user data. If the digital signal includes user data, the digital signal is communicated to a second module over an interconnection path between the first module and the second module. The second module is physically separate from the first module. In the second module, the digital signal is demodulated to yield a data signal, which is communicated the data signal to a data network.
In a further aspect of the present invention, a communications system is provided for communicating data between at least one data system and a plurality of users. The system includes M first modules, each communicably connected to a user via a subscriber line. Each first module includes a signal converter for converting a first analog signal received from the subscriber line to a first digital signal and for converting a second digital signal to a second analog signal for sending over the subscriber line. A first digital connection is connected to the signal converter for sending the first digital signal and for receiving the second digital signal.
The system further includes N second modules, physically separate from the M first modules, where N is less than or equal to M. The N second modules are communicably connected to at least one data system. Each second module has a second digital connection for receiving the first digital signal and for sending the second digital signal. A signal processor is included for processing the first digital signal received from the second digital connection as a first data stream for sending to the data system and for processing a second data stream received from the data system as the second digital signal for sending to the second digital connection. An interconnection path connects the M first modules to the N second modules. The interconnection path communicates the first and second digital signals between the first digital signal connection of the first modules and the second digital connection of the second modules.